Arsenic is a toxic element widely distributed in the Earth's crust and ranked as a class I human carcinogen. Microbial metabolism makes significant contributions to arsenic detoxification, migration and transformation. Nowadays, research on arsenic is primarily in areas affected by arsenic pollution associated with human health activities. However, the biogeochemical traits of arsenic in the global marine ecosystem remain to be explicated. In this study, we revealed that seawater environments were primarily governed by the process of arsenate reduction to arsenite, while arsenite methylation was predominant in marine sediments which may serve as significant sources of arsenic emission into the atmosphere. Significant disparities existed in the distribution patterns of the arsenic cycle between surface and deep seawaters at middle and low latitudes, whereas these situations tend to be similar in the Arctic and Antarctic oceans. Significant variations were also observed in the taxonomic diversity and core microbial community of arsenic cycling across different marine environments. Specifically, γ-proteobacteria played a pivotal role in the arsenic cycle in the whole marine environment. Temperature, dissolved oxygen and phosphate were the crucial factors that related to these differentiations in seawater environments. Overall, our study contributes to a deeper understanding of the marine arsenic cycle. Environmental ImplicationsArsenic is ubiquitous in nature and notorious as poison since antiquity. Currently, the abuse of industrial arsenic products poses a severe threat to human health. Microbial metabolism plays a crucial role in determining the chemical speciation of arsenic. The ocean harbors an equivalent amount of arsenic as terrestrial soil, making it a crucial ecosystem for elucidating the biogeochemical cycle of arsenic driven by the microbial community. The comprehensive understanding of the arsenic metabolic potential in marine environments would contribute to the establishment of efficient management principles for controlling anthropogenic arsenic pollution entry into the ocean, thereby protecting the biodiversity and stability of marine ecosystems.